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Commentary: Nature or nurture

I found out this week that what some folks had suspected was indeed true: I am a Neanderthal.

OK, maybe not all of me. But about 3 percent of me, at least.

You see, recently I became intrigued with an inexpensive genetic analysis marketed by a company called “23 and Me.” It’s a company that tests your DNA for the risk for inherited diseases. It also looks at your DNA to determine where your genes came from.

I found out I had a slightly increased risk for Type II diabetes, for example — but thankfully no identifiable genetic risk factors for cancer, dementia or early heart disease. My ancestry? Primarily European, with a strong Irish component, which is no surprise. Nothing in my genome was very exciting. In fact, my DNA was all pretty boring stuff.

Except for the Neanderthal thing.

According to “23 and Me,” 2.9 percent of my DNA is derived from the DNA of a different species of human being besides Homo sapiens. So while I’m not part alien, I am part cave man.

So what the heck does this really mean?

It seems emerging data suggest that Homo neanderthalensis — Neanderthal Man — lived in what is now Europe and Western Asia between 130,000 and 25,000 years ago. Neanderthals were considerably more physically powerful than modern humans and were particularly well adapted to colder climates.

Contrary to initial concepts about Neanderthal man as a grunting half-man/ half-ape, it is now apparent that Neanderthal man had a complex social structure, engaged in tool-making and ritualistic burials (implying a concept of religion) and actually had a larger brain than modern man.

In 2006, the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, began analyzing the DNA of Neanderthal specimens and found that modern humans and Neanderthal man shared 99.5 percent of the same DNA — including the “modern” version of the FOXP2 gene, which is associated with speech.

The Planck Institute has now sequenced the entire Neanderthal genome and has discovered that among modern non-African humans, unique DNA sequences derived from Neanderthals comprise about 1-4 percent of the modern human genome.

This shows that some interbreeding between the two species did, in fact, occur. Little is known about what significance, if any, this shared DNA has in modern humans. But the mere fact that it is there is fascinating.

All of this made me wonder: What, in fact, makes us human? Are we strictly a collection of genes, a series of woven twists of deoxyribonucleic acid that codes for our every trait? Are we, in the best Calvinist tradition, predetermined towards a certain mindset, a certain outlook and a certain destiny by sheer virtue of our genetic legacy? In other words, is fate all we have?

Or is there something else?

The Neanderthals are all gone, of course. But we modern humans — good old Homo sapiens — have become the masters of this planet in an extremely short time span.

Consider this: In 10,000 B.C., it is estimated the world’s total population was about 1 million people. Humans at this point lived a hunter-gatherer existence, the same sort of lifestyle as their then-extinct Neanderthal cousins.

It was a lifestyle that served as a natural limitation on population growth. Shortly after that time, the advent of organized agriculture resulted in an explosion in human population. By the dawn of recorded history, in 3000 B.C., there were about 25 million people on earth.

The pyramids of Egypt were built shortly after this time. Around the same era Rome was founded, in 753 B.C., the ancient Greeks were having their first Olympiad, and the world contained about 75 million people.

There were about 200 million humans on earth at the time of Christ. The world’s population was still less than 800 million by the time of the American Revolution. By 1900, there were about 1.65 billion people in the world. When I was born, in 1962, there were about 3 billion. And today?

Today, this planet has nearly 7 billion living human beings.

So we have taken over planet Earth. We fly over it and tunnel under it; we’ve cleared the land and paved it over with teeming metropolises. Humans do not just inhabit the earth: we infest it, polluting the air, depleting the oceans and stripping the land of its riches. We’ve even begun to affect the planet’s weather.

In his landmark 1976 book “The Selfish Gene,” Richard Dawkins suggested that humans have become earth’s dominant species primarily because we are intelligent, capable and genetically programmed to be ruthless in our pursuit of what we need to survive and, ultimately, pass on our genetic legacy.

Some doomsayers have predicted the human race will, by virtue of that same selfishness, inevitably allow ourselves to destroy the wonderful planet we call home. It’s our destiny, they say. We simply cannot help ourselves.

But is that all? As humans, are we mere slaves to our internal programming, destined to conquer, to subjugate and ultimately destroy this verdant paradise we call home? Or can we supplant our baser instincts for the greater good? And individually, has my own future been written in some irrevocable genetic script? Is the proverbial die already cast?

I once had a patient, a minister, who was nearly a century old when he died. He lived a long and productive life and was widely perceived as a kind and introspective man. About a year before he died, I asked him a simple question: As a man in tune with the spiritual side of life, what was his perspective on religion?

His answer was short, but profound:

“Why, doc, religion is God’s way of saving us — from us.”

I think that old preacher was a very wise man.

So although our genes make us Homo sapiens, they are an imperfect lens into our own personal futures. Our genes may make us selfish, but we are not rooted solely in our genetic legacy. We can choose to be generous and altruistic. We can choose to be people of good character. We are capable of profound insight and introspection. And it is that capacity for enlightenment, that ability to exercise free will that truly makes us human.

And if I ever backslide, I now know that I can blame it on those sneaky old Neanderthal genes.

Mark Murphy, M.D., is a Savannah physician and writer. Email him at heeldawg@aol.com.